The ever-increasing demand for smaller sized mobile devices, such as cell phones, digital cameras, etc. correspondingly triggered a growing need for a smaller sized photography module, comprising elements such as an optical imaging lens, a module housing unit, and an image sensor, etc., contained therein. Size reductions may be contributed from various aspects of the mobile devices, which includes not only the charge coupled device (CCD) and the complementary metal-oxide semiconductor (CMOS), but also the optical imaging lens mounted therein. When reducing the size of the optical imaging lens, however, achieving good optical characteristics becomes a challenging problem.
The length of conventional optical imaging lenses comprising four lens elements can be limited in a certain range; however, as the more and more demands in the market for high-end products, high-standard optical imaging lenses which show great quality with more pixels are required. U.S. Pat. Nos. 7,920,340, 7,660,049 and 7,848,032 all disclosed an optical imaging lens constructed with an optical imaging lens having four lens elements. The length of the optical imaging lens, which, from the object-side surface of the first lens element to the image plane, are greater than 7 mm. Therefore, there is needed to develop optical imaging lens which is capable to place with four lens elements therein, with a shorter length, while also having good optical characters.